Heretofore, in order to achieve satisfactory adhesion to fiberglass reinforced plastics (FRP) or between a FRP and a metal surface, it has always been necessary to treat the surface of the fiberglass reinforced plastic before applying the polyurethane adhesive. Such surface treatments include a mechanical treatment such as abrading or sanding the fiberglass reinforced plastic or metal surface, a solvent treatment such as scrubbing the surface with a solvent such as methylene chloride, and a chemical treatment as by applying a primer thereto.
The following patents relate to surface treatments which improve the adhesion to fiberglass reinforced plastic surfaces.
U.S. Pat. No. 3,647,513 to Jackson relates to a method of improving the adhesion of a polyester composition to itself or to a metal. This is achieved by treating the surface of the polyester composition such as a fiberglass reinforced plastic with a tertiary amine prior to bonding with a urethane adhesive.
U.S. Pat. No. 3,703,426 to Larson et al relates to using a di- or a triisocyanate as a primer which is applied to a fiberglass reinforced surface prior to bonding with a urethane adhesive.
U.S. Pat. Nos. 3,838,093 and 3,962,498 to Owston relate to priming a fiberglass reinforced plastic with an organic solvent solution containing a partial urethane adduct.
U.S. Pat. No. 4,004,050 to Rabito et al relates to treating a fiberglass reinforced plastic with an organic solvent solution containing an organic polyisocyanate followed by a subsequent treatment of a solution of an organic tertiary amine before bonding with a polyurethane adhesive.
U.S. Pat. No. 4,397,707 to Dawdy relates to a primer composition containing an aromatic polyisocyanate and an amino resin and moisture curing the polyisocyanate compound prior to the application of the adhesive. The composition is used as a surface treatment of fiberglass reinforced plastics before bonding with acrylic adhesives.
The following patents relate to surface treatment and/or polyurethane adhesives.
U.S. Pat. No. 3,714,127 to Fabris et al relates to a sag resistant polyurethane adhesive wherein small amounts of a di- and a multi-primary amine are added to a two-component polyurethane system wherein the equivalent ratio of free NCO to OH is only up to a maximum of 1.15.
U.S. Pat. No. 3,886,122 to Fabris et al relates to a two-component polyurethane adhesive composition which has minimum sensitivity to moisture by limiting the ratio of active hydrogen atoms to isocyanates to from about 1.1 to about 1.9 and hence as an excess of a polyol curing agent.
U.S. Pat. Nos. 3,935,051 to Bender et al and 3,812,003 to Larson et al relate to a two component polyurethane adhesive made from an isocyanate prepolymer and a curative made from a nitrogen containing polyol.
U.S. Pat. No. 4,247,676 to Kimball et al relates to the utilization of an alkali metal salt of MDA (4,4'-diphenylmethanediamine) as a curative.
U.S. Pat. No. 4,336,298 to Schwarz relates to FRP surfaces which are primed with a solution of triphenylmethane dissocyanate in methylene chloride. A curative containing various types of aromatic diamines is used to react stoichiometrically or in excessive amounts with the free NCO groups of the urethane prepolymer.
U.S. Pat. No. 4,373,082 to Kimball et al relates to a curative for a two component urethane adhesive in which the curative is made from a mixture of a polyol and a polyamine with said polyamine being reacted with an organic polyisocyanate to form micelles that exhibit upon NMR examination strong urea peaks and weak urethane peaks. The adhesive desirably has sag resistance. The equivalent ratio of free isocyanate groups to OH groups of the curative is not specified.
U.S. Pat. No. 4,390,678 to LaBelle et al relates to a one component urethane adhesive system which is applied to an FRP. A solid polyhydroxy curative is utilized.
U.S. Pat. No. 4,444,976 to Rabito relates to an improved two-component urethane adhesive which exhibits sag resistance wherein the curative component utilizes a secondary amine such as a dialkyl-N,N'-alkylenediamine.
U.S. Pat. No. 4,552,934 to Rabito et al relates to an anti-sag polyurethane composition utilizing a curative which is made by partially reacting a polyol with an organic polyisocyanate. To the partially reacted polyol is added a small amount of a polyamine, for example ethylenediamine.
U.S. Pat. No. 4,595,445 to Hombach et al relates to a one-component urethane system in which a portion of the free NCO groups are blocked so that the adhesive composition is stable at ambient temperature but reacts at higher temperatures.
U.S. Pat. No. 4,624,996 to Rizk et al relates to a one-component urethane adhesive system in whih the free polyisocyanate is blocked with an oxime compound.
The article "New Urethane Adhesives and Adhesive Sealants for Bonding SMC" by Foreman et al, 35th Annual Technical Conference, 1980, Reinforced Plastics/Composites Institute, The Society of the Plastics Industries, Inc., relates to a primed substrate to which is added a two part urethane system.